International Journal of Environmental Sciences

Volume 3 Issue 3 2012- November 2012    Pages: 1097-1115  <<Previous    Next>>

Diversity and seasonal variations of Class Ascidiacea in Thoothukudi coast, India

Author Information:

Tamilselvi. M1, Abdul Jaffar Ali. H2, Thilaga. R.D3

1- Department of Zoology, V.V. Vanniaperumal College for Women, Virudhunagar – 626 001, India
2- Department of Biotechnology, Islamiah College, Vaniyambadi - 635 752, Tamilnadu, India
3- Department of Advanced Zoology and Biotechnology, St.Mary’s College,Thoothukudi-626 008.


The present study was carried out to record the diversity, abundance and seasonal variations of tunicates for a period of one year (from April 2000 to March 2001) from four different stations situated along the   coast of Thoothukudi, India. Totally 25 species, simple (8) and colonial (17) ascidians, have been recorded. More number of species (19) were recorded at station 1, followed by station 2 (11), station 3 (9) and station 4(6). The abundance of ascidians also varied from 721/m2 (station 1) to 1252/m2 (station 4). More number of species were recorded during premonsoon season at station 1 and less number was recorded during summer season at station 4.Various diversity indices such as Shannon-Weiner index(H’), Margalef’s index (d), Pielou index(J’),Taxonomic diversity index(∆), Taxonomic distinctness index (∆+), Bray – Curtis coefficient (1957) and MDS (Multidimensional scaling) were calculated to analyse species diversity, richness, evenness, average taxonomic distance between two individuals, to compare the diversity between samples, similarity in species composition and stress value respectively. The dominance plot proved the rich diversity of ascidians at station 1 in all seasons.  The dendrogram and MDS plot showed the close similarity in species composition between the samples of Thoothukudi coast. MDS plot illustrated an excellent ordination on the sample collected during all seasons at all stations. In the present study, 95% confidence funnel and 95% probability contours (ellipse) showed lower diversity of ascidians and also polluted nature of the sampling site 3.

Key words: Tunicates, Diversity, Sea squirt, Ascidiacea, Thoothukudi coast.


© 2012 Copyright by the authors, licensee Integrated Publishing Association.This is an open access article distributed under the Creative Commons Attribution License (3.0) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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